Alternating current practice · Mixed difficulty

The peak voltage of 220 volt AC mains (in volt) is

A soft iron rod is inserted in the solenoid. After this what will be the effect on the brightness of the bulb?

Power consumed in A.C circuit is zero then the ac source could be connected to

Statement (A): Step up transformer converts low voltage, high current to high voltage, low current.

Statement (B): Transformer works on both ac and dc.

The core of a transformer is laminated to reduce energy losses due to

A resistor of R=6Ω, an inductor of L = 1 H and a capacitor of C=17.36 μF are connected in series with an AC source. Find the Q - factor.

A bulb rated $60 \mathrm{~W}$ at $220 \mathrm{~V}$ is connected across a household supply of alternating voltage of $220 \mathrm{~V}$. Calculate the maximum instantaneous current through the filament.

Consider an a.c circuit having resistor of resistance $R$ and an inductor having reactance $X_L.$ If voltage leads the current by an angle $60^{\circ},$ then

An LC current contains inductance $\mathrm{L}=1 \mu \mathrm{H}$ and capacitance $\mathrm{C}=0.01 \mu \mathrm{F}$. The wavelength of electromagnetic wave generated is nearly :-

A 220 V, 50 Hz ac source is connected to an inductance of 0.2 H and a resistance of 20 ohm in series. What is the current in the circuit

Statement I: In a series $R-L-C$ circuit the voltage across-resistor, inductor and capacitor are $8 \mathrm{~V}, 16 \mathrm{~V}$ and $10 \mathrm{~V}$ respectively. The resultant emf in the circuit is $10 \mathrm{~V}$.

Statement II: Resultant emf of the circuit is given by the relation $E=\sqrt{V_R^2+\left(V_L-V_C\right)^2}$.

A step-up transformer is used on a 120 V line to provide a potential difference of 2400 V. If the primary coil has 75 turns, the number of turns in the secondary coil is

Assertion(A): Two identical heaters are connected to two
different sources one DC and other AC having same
potential difference across their terminals. The heat
produced in heater supplied with DC source is greater.

Reason (R): The net impedance of an AC source is
greater than resistance.

A lamp (pure resistance) is connected in series with a capacitor

A) When a dc source is connected to the combination, the lamp will not glow in steady state

B) When ac source is connected to the combination, the brightness of glow of lamp increases with increases of frequecncy of ac.

A Daniel cell is connected to the primary coil of a transformer. If the output voltage of the Daniel cell is $10 \mathrm{~V}$, and the ratio of secondary to primary coil turns of transformer is 2 , then the voltage in the secondary will be

A charged capacitor is discharged through a resistance. The time constant of the circuit is $\eta$. Then, the value of time constant for the power dissipated through the resistance will be

A $16\,\,\mu F$ capacitor is charged to a $\mathrm{20}\,\,\mathrm{volt}$ potential. The battery is then disconnected and pure $40\,\,mH$ coil is connected across the capacitor so that $\mathrm{LC}$ oscillations are setup. The maximum current in the coil is

For a series $L - C - R$ circuit with $R = 100\,\Omega$, $L = 0.5\mathrm{ mH}$ and $C = 0.1\,\mathrm{pF}$ connected across $\mathrm{220V} - 50\mathrm{ Hz\, AC}$ supply, the phase angle between current and supplied voltage and the nature of the circuit is

Assertion: In series LCR circuit phase difference between current and voltage is never zero.

Reason: Voltage and current are never in phase.

A capacitor of capacitance $100 \, \mu \mathrm{F}$ and a coil of resistance $50 \, \Omega$ and inductance $0.5 \, \mathrm{H}$ are connected in series with a $110 \mathrm{~V}, 50 \mathrm{~Hz}$ AC source. Find the rms value of the current.

A $500 \mu \mathrm{H}$ inductor, $\frac{80}{\pi^2} \mathrm{pF}$ capacitor and a $628 ~\Omega$ resistor are connected to form a series LCR circuit. Calculate the resonant frequency and $Q$-factor of this circuit at resonance

Voltage and current in an ac circuit are given by $V=5 \sin \left(100 \pi t-\frac{\pi}{6}\right)$ and $I=4 \sin \left(100 \pi t+\frac{\pi}{6}\right)$

$A$ radio set operates at $6 \mathrm{~V}$ DC. A transformer with 18 turns in the secondary coil is used to step down the input 220 V AC emf to 6 V AC emf. This AC emf is then rectified by another circuit to give 6 V DC which is fed to the radio. Find the number of turns in the primary.

The power in ac circuit is given by $P = {E_{rms}}{I_{rms}}\cos \phi .$ The value of $\cos \phi$ in series LCR circuit at resonance is

Power factor of series LCR circuit at resonance is

A transformer steps up an A.C. voltage from 230 v to 2300 v. If the number of turns in the secondary coil is 1000, the number of turns in the primary coil will be

In an ideal choke, ratio of its inductance L to its DC resistance R is

By what percent the impedance in an series LCR, AC circuit should be increased so that the power factor changes from $\left( {1/2} \right)$ to $\left( {1/4} \right)\,?$ (assume resistance $R$ remains constant)

Assertion: When capacitive reactance is smaller then the inductive reactance in series LCR circuit, voltage leads the current.

Reason: In series LCR circuit inductive reactance is always greater then capacitive reactance.

A resistance R, inductance L and capacitor C are connected in series to an oscillator of frequency $f$. If resonant frequency is $f$, then current will lag the voltage when